Conventional wisdom suggests that if you live in an area devoid of fresh, healthy food, you won't eat well. These so-called food deserts, the logic goes, are a root cause of the obesity epidemic.
But new research indicates that the picture is much more complicated, with food choices being affected by several factors, including the cost of food, cultural preferences and marketing. Eliminating food deserts, researchers say, may only marginally improve people's health.
"I wouldn't put it at the top of my policy agenda," said Roland Sturm, a senior economist at the Santa Monica-based Rand Corp.
He and his colleagues published a study this month in the journal Preventing Chronic Disease that found virtually no link between the type of food and drinks that Los Angeles County adults consume and the proximity of fast-food outlets, grocery stores and convenience stores to their homes. In the last few years, he has published other papers evaluating the connection between the food environment — the distribution and number of food shops — and people's eating habits and, for the most part, found little connection.
Other experts say that the findings aren't necessarily surprising because it's hard to pinpoint a single cause of bad eating habits. However, they maintain that the food environment can affect what people eat and that healthy and convenient choices are vital to improving public health.
"It would be a mistake to conclude that the food environment is not important," said Dr. Paul Simon, director of the Division of Chronic Disease and Injury Prevention at the Los Angeles County Department of Public Health. The study was conducted by researchers from Rand as well as from the county health department, but Simon was not involved.
The research was limited. It looked only at a few variables — such as fruit and vegetable intake and soda consumption — and at study subjects' proximity to stores. It did not factor in the types of food those stores offered or food options people might have in other parts of their lives, such as work.
Still, Simon agreed that government regulations intended to improve public health tend to be simplistic. Dropping a new supermarket in an underserved community won't solve dietary problems, he said. Supermarkets sell unhealthy foods, and the most unhealthy ones tend to be marketed most heavily, he said.
Combating obesity requires a multi-pronged approach that includes education and changing attitudes. He cited the anti-smoking campaign of the 1960s and 1970s, which successfully changed tobacco culture in the United States.
"Beyond just giving people information, we have to actually change social norms," he said.
The study released last week evaluated 150 effects that food environments could have on people's health and found only two that were statistically significant. For the most part, there was no connection found between the location of certain kinds of food stores — whether it be a fast-food outlet a block away or a grocery store a mile away — and how much soda or fruits that residents consumed per week, or whether they were overweight.
Harold Goldstein, executive director of the California Center for Public Health Advocacy, said the study included only a partial representation of a neighborhood's food environment. For example, the researchers — who used data on about 5,000 people's eating habits — evaluated whether the presence of a convenience store within half a mile of a subject's home affected how much soda they consumed per week.
Goldstein said a more effective way of evaluating the food environment is to look comprehensively at the type and quality of a neighborhood store's offerings.
His center conducted a study in 2008 that calculated a ratio of fast-food and convenience stores to grocery stores and produce vendors in various neighborhoods, and measured that against the prevalence of obesity and diabetes. "You put all of that together and it's a strong correlation," he said.
That study found that counties with the highest ratios of fast-food outlets also had some of the highest rates of obesity and diabetes. For instance, San Bernardino County had the highest proportion of fast-food restaurants to grocery and produce stores in the state — and an obesity rate of 27.2%. Marin County had the lowest ratio of fast-food establishments in the state and an 11.4% obesity rate.
He said that if his center conducted its study using the same methodology as the Rand researchers, they would not have seen a correlation between obesity and the food environment.
"It would be unfortunate if a study like this were to be taken at face value to mistakenly suggest that the food that's available in people's communities doesn't have any impact on their well-being," Goldstein said. "It's a more sophisticated an analysis to be able to show that what we intuitively know to be true is true."
Susan Babey, senior research scientist at the UCLA Center for Health Policy Research, agreed that it makes more sense to broadly evaluate a neighborhood's food options, and to account for variation from store to store. A supermarket in one neighborhood could be filled with fresh produce, while a supermarket in another may not be.
Sturm, the RAND researcher, maintains that the food environment is not that important, especially in a highly mobile society such as Los Angeles, where people travel great distances every day. "So even if you don't have a supermarket in your block, it's really not going to be that far away," he said.
In 2008, Los Angeles lawmakers banned new fast-food restaurants in South Los Angeles as part of a campaign to improve residents' health. The law aimed to stem high rates of obesity and diabetes that afflict African American areas.
Sturm published a study earlier this year that found that from 2007 to 2012, the percentage of people who were overweight or obese increased everywhere in Los Angeles, but the increase was significantly greater in areas covered by the fast-food ordinance, including Baldwin Hills and Leimert Park.
"There is just nothing easy. That's the problem," he said.
Clare Fox, executive director of the Los Angeles Food Policy Council, said there's no single solution to the obesity epidemic. However, she said she feared that studies such as Rand's discount the importance of fighting for healthy food options. There are long-standing disparities in food access across neighborhoods, she said.
She said advocates should be "empowering stores that are residing in low-income communities to market and brand healthy food in new ways so that we can interrupt these systemic and historic inequities."